Phase balancing system



p 1 1953 E. F. w. ALEXANDERSON 2,652,529

PHASE BALANCING SYSTEM Filed Sept. 17, 1952 Fig.1, I

Fig.2

SINGLE PHASE LOAD PHASE PHASE FTER SH! 2 Fig. 5

K L3H SHEER I2 Inventor:

Ernst FiWAlexandeFson,

Patented Sept. 15, 1953 NITED srATiE-s PAT ETIN'T O FF I- C 'E PHASE SYSTEM' "Ernst F. Alexanderson, Schenectady, N. Y.,

asslgnor to General Electric Company,a corporation-of N ew'York Application September 1'7, 1952, SerialNo. 310,073

lit Claims. 1

My invention relates to phase balancing systems and, more particularly; to an arrangement for maintaining a substantiallybalanced load condition in'a polyphase'systemtc'which is connected'. a variable single phase load.

"If a single'phase load is connected to one phase oi av polyphasei power system" there 'will be a tendencyfor the'system load" to -be unbalanced. A capacitive reactance; an inductive reactance and a single. phase load can be energized from-different phasecond'uctors of a three phase system and by suitable choiceoicornponents, a' balanced condition can beestablished. Such a condition in'known arrangements can not persist-ii the magnitude of the single" phase load changes appreciably.

It is an object of .my invention to provide a control system for use in conjunction with a load balancing arrangement'for a three'phase power system to .one phase of which'is connected a variable single phase load.

'It is a further object of my invention to provide an automatic load balancing systemwhich is adapted to maintain balanced load conditions in'a three phase system to which is connected one or more variable single phase'l'oa'ds.

"It'is a still further object "of my invention to provide an arrangement for automatically transferring power from one phase of'a three phase system to another in'response to variations in the load applied to'one or'more phases ofthe three phase system.

In accordance Withthe invention capacitive reactance meansan'd inductivereactance means such as anon-linear reactor are'energized'from different phases'of apoiyphase source or electric energy and are arranged so I that for balanced conditions no net or" resultant leading and lagging currents are respectively drawn fromth-e system bythe'capacitive and 'inductive reactances. As an'unbalanced condition of the polyphase' source "develops, due to unbalanced loading for examplemcontrol means responsive to the unbalanced eontlition causes the i capacitive reactancemeans'todraw leading current from itself, however, both-as to its organization and method of operation, together with further" objects-andadvantages thereof may best be understoodby reference to the-followingdescription taken in connection with the accompanying drawing in "which'Fig. 1- thereof is a circuit diagram illustrating schematically a phase balanc'er applied toa three phase source of energy in accordance with my invention; Fig. la is-a vector diagram toaidin understanding-the principles of the invention} Fig, 2- is a modification of Fig. 1 and illustrates a particular'application of my invention operable over wider ranges of phase unbalance than the-arrangement-of Fig. l; and in which Fig. 3' represents'schematically' an alternatitre-"arrangement utilizing the'princi-ples of the invention.

In the'arrangementpf l ig. 1, power is drawn by the single phaseloa-d, indicated schematically, from lines band 3 tending to cause unbalanced loading of the three-phase source comprising lines I, Tan-d 3. 'To' compensate for this unbalanced loading, capacitance means C andinductance 1 means R are respectively connected acrossconductorsf and 3 and across conductors land: of-the t'hree'phase-system. To provide control of'the "magnitudes of reactanceof-elemen-ts C and R continuously'and' for varied loading "conditions, means including 'an electronic equipment' 4"- may be employed. The electronic equipment '4 functions as a variable'reactance c'rrcuit'which regulatesthe capacitive reactance of the 'capacitor'C'in response to variations in the load. Therea'ctor-R is or the type in which the inductive reactance thereof can be varied by a saturating current which may be derived from theelectronicequipment 4. "Thus, by controlling the operation ofthe electronic-equipmentl in responseto'load'variations, the effective capacitance inductance of "elements C and R- may be varied to maintain proper balancing of the variousphases 'ofthe'powersupply.

' The electronic -equiprnent or reactive control means 4' comprises gaseous discharge rectifier elements -5- 8= arranged in abridge circuit with the capacitor C connected by means of reactors 9 and Hi to one diagonal of the bridge and with control =w-inding I I I connected V across 1 the wother diagonal thereof. Thetubes FB-are arranged to provide w ll wave: rectification of -the alternating voltage impressedaacross capacitor C: from lines Land: of the power 'source.

xwinding "-l,.=l 'acomprisesa saturating control winding for'reacter rand-is connected in'series withwthe'directcurrent output circuit of the electronic equipment 4 for controlling the reactance of inductive reactor R. Reactor R is provided with another saturating control winding i2 which affords a constant degree of presaturation and is energized by a direct current exciter I3 or any other suitable direct current source. The constant saturating current in Winding I2 and the variable saturating current in winding I I produce opposing control effects on the reactance of reactor R. Preferably, the constant and variable saturating currents are adjusted so that for zero load on conductors I and 3 the net resulting control effect is zero and the current through winding II is equal to the maximum rectified current that can be delivered by the electronic equipment 4. This maximum current of the electronic equipment 4 in flowing through reactors 9 and I8 is also preferably of such magnitude and phase as to neutralize the current of the capacitor C. Since this condition obtains for zero load in the single phase line I4, no power could be transferred from one phase to the other because current in reactor R, and net current in capacitor C and reactors 9 and III, are substantially zero.

When a single phase load such as is indicated is applied to transmission line I4 loading of the polyphase system will tend to be unbalanced and will cause a control signal to be supplied to the control electrodes of tubes 58 for controlling the conduction of these tubes in accordance with the magnitude of the single phase load. This signal may be supplied by a current transformer I5 which derives a signal which varies in accordance with variations in the current drawn by single phase line I4. The control signal is then applied to a phase shifting circuit I6 which operates to control conduction of tubes 5-8 in accordance with the magnitude of the current in line I4. Circuit I6 comprises any well-known arrangement for varying the phase of the grid signals of tubes 58 with respect to the alternating plate voltage. The control signal can also be obtained from the voltage changes across lines I and 3 caused by load I or may be obtained from a combination of these two arrangements. Fig. 1 shows this combination wherein an additional signal depending on the voltage existing across phase conductors I and 3 is supplied through potential transformer IT to the input of phase shifter I6 in addition to the signal derived F current passing through tubes 5-8 to a corresponding degree thereby to reduce the variable saturating current in control winding II. This allows the constant presaturating current supplied to control winding I2 to increase the saturation of reactor R thereby decreasing its reactance and increasing its lagging current. Reduced current through tubes 5-8 and through reactors 9 and I0 renders capacitor C effective to draw leading current. The net leading current in capacitor C and the lagging current in reactor R respectively drawn from the hases comprising conductors I and 2 and conductors 2 and 3 appears as a resultant energy current which is supplied to the phase comprising conductors l and 3 to which the single phase load is connected. Thus reactor R and capacitor C are effective to cause an interchange of energy between the phases so as to maintain balanced conditions. This interchange of energy is represented for one condition in Fig. la wherein vector rotation is counterclockwise with the current Ixc leading the voltage E2 by ninety degrees and with the current IXL lagging the voltage E 1 by ninety degrees. The resultant current Ir of these two quadrative currents has an energy component relative to the load voltage E3.

The electronic equipment has been shown in its simplest form to comprise four rectifying tubes 58 connected as a single phase, full wave rectifier arranged to control both reactor R and capacitor C. In order to reduce the generation of harmonics in the electronic equipment, it may be desirable to employ several additional groups of rectifying units such as I8 and I9, similar to the unit comprising tubes 5-8, as shown in Fig. 2 so that the several groups can be fired at different phase relations relative to the power supply by means of the adjustable phase shifting circuits I6, and 2|. In Fig. 3 the reactors 9, I0. and R, the transformer I1, and the presaturating winding I2 are connected as in Fig. 1.

In the embodiment of the invention as shown in Fig. 3, the phase balancing circuit comprises a step-down transformer for connecting the capacitor C and reactor R to the three phase system. The transformer is provided with a Y-connected primary 22 and a delta connected secondary 23 so as to short circuit the third harmonic. The load is supplied by a Scott connected transformer 24.

The reactor R and capacitor C and electronic equipment 4 are employed in a manner similar to that described in connection with Fig. 1 above. The control signal applied to the phase shifter preferably should be derived from the voltage across winding B of the delta transformer winding 23. If there is an excess amount of power drawn from phase B by the single phase load schematically represented as an electric locomotive, the electronic balancer operates in the manner described in connection with Fig. 1 to take current from the other two phases in the delta connected secondary winding 23 and deliver it to phase B of the delta winding and in g turn to phase B of transformer 24.

If the engine moves along its track toward the left its load is transferred from phase B to phase A. Such a shift in the load makes it necessary to interchange the connections of capacitor C and reactor R. To this end rectifiers 25 and 26, polarized relay 21, and auxiliary relays 28 and 29 are used, rectifier 25 being energized from lines 2 and 3 and rectifier 26 being energized from lines I and 2. Polarized relay 21 is provided with a pair of coils 30 and 3| which are respectively energized by rectifiers 25 and 26. The magnitude of voltage supplied to coils 30 and 3|, together with the action of polarizing coil 32, determines whether the contact 33 engages the contacts 34 or the contacts 35 which respectively control the relays 28 and 29. Thus if relay 28 is operated, reactor R. and capacitor C will be connected across winding 23a, and 230 respectively. If, on the other hand, the voltages between lines I and 2 and between lines 2 and 3 are such as to cause contacts 34 to be closed. then relay 28 will operate and will cause the reactor R and capacitor C to interchange connections so as to establish balanced conditions.

In view of the above description of the invention, it will be understood that in accordance with the invention, smooth balanced conditions may be maintained in a polyphase system wherein the loading is such as to tend to unbalance the system.

While-.1; have. 2 shown eertaina embodiments .;9 mydn-ventim by way; at dilustratiqmcmany mo di fications will occur to those skilled in the art and I therefore.- intend 3 in the -.appende d claims to cover: all such: medificationsrasr fall within the true spirit and scope of my invention. I

- What. I claim. new and-desire =tc secure -by hetters=-1 atent on the United-States is v 1c in combination a non linear reactori anda capacitor arranged to beenerg ized. from rdifierent phases of as pclyphase system; a bias-winding.-.for aaid'non-linear reactor. energized with,direcircur rent of substantially: constant magnitude; a. control winding for said non=linear --reactor-, L the magnetizing: action or said control winding. being in.:opposition=tc the magnetizing actionvof. said bias winding, a rectifier circuit :energized with alternatin'gi 'curi'entiufrurh the.-. terminals: of said capacitor an'diccnnected; wsupplwdir'ectcurrent to; said" wmrerwmum ana means responsiveco unbalanced. loadingu'oi the ipclyphase' system tor controlling lithe :rmagnitude cot current athrcugh said. mtifiervcircuit.

m2; macombinatiomia nmr-tlinean'reactonandia capacitor arranged tozb'e energized from different phases of as polyphase system; a.:biaszwindingi .rcr saidunonlinear reaotorzenergizd with directeur rentpfssubstantiall y'cconstant ma'gnitude, ...'a;-c0n =tro1 winding Y. fcr zz'saidimon-linear reactor, i the magnetizingiaction fssaidcontrol winding being imcppo'sitiomato aheumagnetizing action 0f said bias wind-ingyi.atrectifierxcircu-it Jenergiz'ed 'with alternatingscurrntufrbm; the terminalsf said capacitor andcdnnectedltc supply. direct current to said icontrbl iwinding, the; bia'sing action of saidr bias winding:beings.substantiallyequal to themagnetizing action ofssaid :eontrol -=windng when .thexun'entsinzsa-i'd: control: winding issubstantially equah to .thezhiaxiinum current that said rectifierxcircuit is capable ofz deliv'ering and means" responsive-i to-' unbalanced loading ofv the polyphases :systemlfor; controlling the magnitude of.- current through said rectifier-circuit.

3.. Inxombinatidne.ahoniinear reactor and a capacitor. arrangedlta lee-energized fro'rmdifierent phases not; aipoly pha'se a wiudm'g mr saidr-nonelinear reactor energized 'withdire'ct cur-' rent of substantially constant magnitu'de 'c'd'ne saidirbi'a'shwindin'g a rectifier .mrcumeaergrzea with alternating. current: frrom...the terminals 1 of said acapacitorr. and connected: =tb.-. supply direct current. .to: :saidrontrohMinding, tiie maiiiinum current which'isa-idfzrectifler bircuit is capabieer delimiting. beings slflfistai'i'ti'all-y equar tef ilh "current-.i'eduiredikto' neutrafize the euerenr insa id capacitor, and :meansresponsive :t'o unbalanced loading; of/cthe' system for commune themagnitudelot current throughfiiii rectifier circuit. 1 g I r :4: in combination;ainonalineai and; capacitor arranged to be lener gize cvfrom iiiifer'ent phases bfia -polyplias systema saiuinomnnear reacbcrenergieeu withfiiiect rent of sulistafitially' magn 'itude; anon; ecwirmmg frcannon-linear reactor; meme" naming-amen or sara cehtror wifiame mm m bppos'itib *t'o the-rfianetiaihgaenbnei said bias rectifier eireuirener'grzeuwith inter ma net sm the teifiiifials arsed-capacji'to'r andc'dniieifiied""to' siipplyfdirect cfirfijiit {to em re i e e i :bias winding being substantiallyeequal ate the magnetiaingectionoi said control-windingvwhen the, current in said control-winding yiszsubstan tially equal tothe maximum' current; that said rectifier.- circuit is capable of delivering; the-1118K imum- 6111161162: which: said: rectifier-. circuit: descapahle of delivering; being substantially. to the; current required to rneutralizewthe currentvin said; capacitor, and .mcans responsive; to: unbab anced- -leading:of1 the polyphase. system iEoncen-t trolling the magnitude of currenttthrough said rectifiergcireuit:

5'. In -combination-, ianonalinear: reaeton-zand-a capacitoriarranged tonbe energized fromid-iiferent phases of a, pqlyphase; system, .a bias *windin'g fromsaid non-linear reactorenergized with: direct current: .of substantially; constant :magnitude,-: .a control winding fora-saidanonslineai' reactonnthe magnetizing action rot saidcontrol. .winding being in opposition to thewnragnetizing vaction-of Said bias winding, a rectifier circuit energized-with alternating current. .from" the terminals: ofcsaifi capacitor and. connected; torsupplyflirect. current to said controlwinding, means responsiv'eztaim balanced.- loading ofzthe; polyphase system; m1- controlling the magnitude piscurrentthrough said-rectifier circuit, and means-responsive unbalanced load on the system forzinterch'an'giflg the connections of saidsrea'ctor and. bilSHi'Q-UBF pacitor;

.6. In combination,..atnonelinear'weactoiflw i capacitor arranged totbeenergized crewman-ant phases of a polyphasesy'stem, a bias wind-infiifi said non-linear reactor :aienerg-ized --With direct current of substantially constant. ma gin-mama control winding: for. sai'd' non lin'ear rear-awe, magnetizing action of said control w nd i-ii being in opposition; toxthe: magnetizingaction of said bias winding, .9. rectifi'er circuit energized with alternating current: from the terminals ar se-m capacitorzandxebnnecteclto supply iiirt cufl'iiflt to; lsaidwcontrolawindingt the-manna afion of bias winding being substantially equal to the magnetizing action of said control windiiag when the. current..;-in ."said. control winding ds substrate-- ti-ally. equalt-to the-maximum current thats'aid rectifier; circuit: is. capable or deli yeriiigizmeahs responsive toiunbalan'eed "lea n2 er t ta -poi? phase: systemi .forr. contr'ol lin gthe mag tude r55! current through 'said re'ctifie t -"and responsive. man unbalanced 'l' the system forinterchang'ingthe connection cream reactorand of" .said capacitor.

: 7.. in combinationr-a nonqinear reactor and-a capacitor. arranged tobe energized from=-differerit phasesmf a polypha'se-systern, a: bias winding for said-.non-linear reactor energized with directc'ur rentof substantially constant magnitude; acorntrol windingfo'rsaid non-linear i'fii'ifOi", the mag; netizing action of said control nd'mgbemg'in opposition tolth'emagnetizing hammer-sale Bias winding;a:a: rectifier circuitenergized with altei natin'g: current from the terminals cFsaid'capacitor and connected to supply direct current tosaid controli-windihg, I themaximum 'eurrent which said rectifiercircui riscapabi'e ef del ing being substantially equal to thecurrem'reqa ed sementralize; thevc'ur'rent in said capacitor; -me'an's 'ie sponsi've tovuunbalanced loading of the polyphase system for:-contro1ling theima'gnitude or current h ugh said --rectifier:'circuit-,. andr'm'eans :respon sive to-an unbalanced-.load;=on whe -system oi' interchanging the *COIIIIGCtiDfiSIOf-Sfiiid lreactoniintl of sai dcapaci-tor. V

...8...In. combination; a rnon-linearwreadton and-a capacitor arranged to be energized from different phases of a polyphase system, a bias winding for said non-linear reactor energized with direct current of substantially constant magnitude, a control winding for said non-linear reactor, the magnetizing action'of said control winding'being in oppositionfto the magnetizing action of said bias winding, a rectifier circuit energized with alternating current from the terminals of said capacitor and connected to supply direct current to said control winding, the biasing action of said bias winding being substantially equal to the magnetizing action of said control winding when the current in said control winding is substantially equal to the maximum current that said rectifier circuit is capable of delivering, the maximum current which said rectifier circuit is capable of delivering being substantially equal to the current required to neutralize the current in said capacitor, means responsive to unbalanced loading of the polyphase system for controlling the magnitude of current through said rectifier circuit,: and means responsive to an unbalanced load on the system for interchanging the connections of said reactor and of said capacitor.

9. An arrangement for'maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, and means responsive to variations in a quantity which varies as a function of a load energized from still another phase of the polyphase source for controlling the effective reactance of said capacitive reactance means and of said inductive reactance means.

I 10. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance meansenergized by a quantity which is representative of one phase of the polyphase source, inductive reactance means energized by a quantity which isrepresentative of another phase of the polyphasesource, and means responsive to variations win a quantity which is indicative of changes in the loading of still another phase of the polyphase source for controlling the eflective reactance of said capacitive reactance means and of said inductive reactance means.

11 .An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, and means responsive to variations in a quantity which varies as a function of a load energized ifrom still another phase of the polyphase source for increasing the leading and lagging current drawn respectively by said capacitive reactance means and by said inductive reactance means in response to an increase in the magnitude of said load.

12. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, and means responsive to variations in a quantity which varies as a function of a load energized from still another phase of the polyphase source for decreasing the leading and lagging current respectively drawn by'said capacitive reactance means and by saidinductive reactance meansin response to a decrease in the magnitude of said load.

' 13. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, reactive control means arranged in parallel with said capacitive reactance means for controlling the effective capacitance of said capacitive reactance means, and means responsive to variations in load applied to still another phase of the polyphase source for controlling the effective reactance of said inductive reactance means and or said reactive control means.

14. An. arrangement for maintaining substantially balanced loading of a polyphase sourceof electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, reactive control means arranged in parallel with said capacitive reactance means for controlling the effective capacitance of said capacitive reactance means, a control winding for said inductive reactance means, said winding being in series with said reactive control means, and means responsive to variations in load applied to still another phase of the polyphase source for controlling the fiow of current through said reactive control means and through said control winding.

15. An' arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, electronic means in parallel with said capacitive reactance means for controlling the effective capacitance of said capacitive reactance means, a control winding for said inductive reactance means, said winding being in series with said electronic means, a biasing winding for said inductive. reactance means, said biasing winding being arrangedso that the biasing effect thereof is in opposition to the magnetomotive force of said control winding, and means responsive to an increase in load on still another phase of the polyphase source for decreasing the flow of current through said electronic means and through said control winding.

16. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, electronic means in parallel with said capacitive reactance means for controlling the effective capacitance of said capacitive reactance means, a control winding for said inductive reactance means, said winding being in series with said electronic means, a. biasing winding for said inductive reactance means, said biasing winding being arranged so that the biaising efiect thereof is in opposition to. the magnetomotive force of said control winding, the current through said control winding and said electronic device being of such magnitude for zero load on still another phase of the polyphase source that the bias of said control winding is substantially equal to the bias of said biasingwinding'and so that the capacitive reactance of said capacitive reactance means is substanti'allyofiset by the inductive reactance of said electronic means, and means responsive to an increase in load on said another phase of the polyphase source for decreasing the flow of current through said electronic means and through said control winding.

17. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, and means responsive to variations in a quantity which varies as a function of the voltage across still another phase of the polyphase source to which a single phase load is connected for controlling the effective reactance of said capacitive reactance means and of said inductive reactance means.

18. An arrangement for maintaining substantially balanced loading of a polyphase source of electric energy comprising capacitive reactance means energized from one phase of the polyphase source, inductive reactance means energized from another phase of the polyphase source, and means responsive to variations in a quantity which varies as a function of a load energized from still another phase of the polyphase source and 01 the voltage across said another phase for controlling the effective reactance of said capacitive reactance means and of said inductive reactance means.

ERNST F. W. ALEXANDERSON.

No references cited. 

